Air conditioning apparatus



Sept. 22, 1942.

C. M. SANDERS, JR

AIR CONDITIONING APPARATUS FiledJuly 2, 1938 2 sheets-Sheet 1 INVENTOR`Cl-mlzm-:s M. SANDERS, JR.

WITNEssEs: 7?. (L

ATToRNE' Sept- 22; 1942 c. M. SANDERS, JR 2,296,741

AIR CONDITIONING APPARATUS Filed July 2, 1938 2 sheets-snet 2 wwwwlTNEsSEs: y lNvENToR LVM/b CHARLES M.5ANDER5,JR

#6 FJG. 2. BY

- y ATTORNE;

Patented Sept. 22, 1942V 2,296,141 .un CONDITIONING ArrAaA'rUs CharlesM. Sanders, Jr., Oak'Park, Ill., assignor to Westinghouse Electric &Manufacturing Company, of Pennsylvania East Pittsburgh, Pa., acorporation Application July 2, 1938, Serial No. 217,117

c claims;

My invention relates to air conditioning apparatus, and it hasfor anobject to provide improved apparatus.

A further object is to provide improved air conditioning apparatusadapted for operation at partial load to maintain more readily a desiredtemperature of the air in the enclosure.

A further object is to provides. simpler and more flexible method ofcontrol, providing a better balance between the amount .of coolingprovided by the apparatus and the cooling load of the air conditionedenclosure.

In accordance with my invention, air withdrawn from the enclosure ismixed with outdoor air. One or more cooling elements are disposed vinthe path of the outdoor `"air before mixture,. and one or moreadditional cooling elements are disposed in the path of the mixed' airstream for cooling at least a portion of said stream. Another portion ofthe mixed air stream may be byepassed around the latter cooling element.The mixed air stream is then delivered to the enclosure.

The apparatus is preferably. provided with a thermostatic control whichis subjected to the temperature of the airlin the enclosure and isarranged to initiate operation of the cooling elements in the outdoorair stream successively and then the cooling elements inthe withdrawnair successively as vthe temperature reaches successively higherpredetermined values. A further thermostatic control may be provided toterminate operation of theoutdoor air cooling ele- Aments as the outdoorair.v temperature drops,

leaving the air cooling elements in the mixed air stream to carry thecooling load.

The above and other objects are effected by my invention as will beapparent from the following description and claims taken in connectionwith theaccompanying drawings, forming a part of this application, inwhich:

Fig. 1 is a diagrammatic View of an air conditioning system arranged inaccordance with my invention; and,

. Fig. 2 is a similar view ofv a secondY embodi- Referring to thedrawings in detail, an enclosure to be air conditioned is indicated atI0. Air is withdrawn from theenclosure through a duct Hand conveyed toan air conditioning chamber l2. Outdoor air is conveyed through a ductI3, an air conditioning chamber I4 and a duct I5 to the duct il, inwhich it is mixed' with the return air and ows therewith through thechamber I2 anda duct Ii to the enclosure III. The

(Cl. B2-6) air described is effected in any suitable manner, as by meansof fans I4' and I5' arranged in the chambers I 4 and I 5, respectively.

The present air conditioning system includes two refrigerating systemsindicated generally at I1 and I8, each including a motor compressor unitI9 and a condenser 20. It also includes an expansion valve 20' of anysuitable type known in the art, lfor example, a thermostatic expansionvalve which operates in response to the superheat of the 'vaporizedrefrigerant discharged from the evaporator. The refrigerating system I1includes an evaporator 2| disposed in the chamber Il and extendingentirely across the outdoor air streamflowing therethrough. The

system I8 includes an evaporator 22 disposed in the chamber I2 andextending partially across the mixed air stream. A by-pass 23 may beprovided, if desired, between the evaporator 22 and the adjacent wall ofthe chamber, through whichl by-pass a portion of the mixed air streammay ow without being cooled. A

The evaporator 2i and its refrigerating system I1 are preferably of acapacity to take care Y of the cooling loads which depend upon thetemperature of the outside air, that is, the loads due to transmissionor leakage of heat, any inltration of outdoor air, and admission offresh air to the enclosure. The evaporator 22 and its refrigeratingsystem I8 are preferably of sumcient capacity to take care of the loadswhich do not depend on the outside` air temperature, for example, sun`load, light load, and occupant load.

The control comprises a thermostatic switch T1 which isresponsive to thetemperature of the withdrawn air flowing through the duct Ii and isarranged to close its contacts 2Q and 25 successively as the temperatureof the withdrawn air rises to successively higher predetermined values,which -diiler but slightly and represent substantially the temperaturedesired to be maintained in the enclosure I0. A second thermostat T2 isresponsive to the temperature of the outdoor air before it passes overthe Vevaporator coil 2i, and is arranged to open contacts 26 as thetemperature of the outdoor air decreases below a predetermined value.The latter predetermined value represents the temperature of the outdoorair at which the entire heat load can be taken careof, by the evaporator22. -If

the evaporators are proportioned as. suggestedV iiow of 55 pendent uponoutdoor air temperature, then such by the evaporator 2 through thechamber I2,

predetermined value is the temperature desired to be maintained withinthe enclosure I0. The thermostats are of any suitable type known in thevart and, of course, are adjustable.

'The refrigerating system I1 is controlled by a circuit which extendsfrom the line conductor L1 conductor La. 'I'he control has been shown ina simplified manner in order tha-t the inventive thought may be morereadily understood, and it is to be understood that the usual expedientsand instrumentalities used in the. control of apparatus of this nature,including relays, protective devices, are to be used in the usual mannerin which such expedients and instrumentalities are commonly used in theart.

Operation Assuming the contacts 25 of the thermostat T2 to be closed byreason of a sufliciently high outdoor temperature, the operation of theevaporators is controlled by the thermostat T1 in response to thetemperature of the air in the enclosure I to maintain said temperatureat substantially the desiredvalue. A demand for cooling is Yindicated bya rise in temperature in the enclosure. As the temperature reaches ther`st predetermined value, the contacts 24 close, completing the circuitfor the refrigerating system I1. Operation of thev latter is effected tosupply refrigerant to the evaporator 2|, which serves to cool all of theoutdoor air passing through the chamber I4. The temperature not yethaving reached the second predetermined value, the contacts 25 are open,rendering the refrigerating system I8 of the evaporator 22 inactive. Inthis case, therefore, the outdoor air is cooled and dehumidiiied by theevaporator 2l, mixed with air withdrawn from the enclosure, and themixture is delivered `Without' further cooling to the enclosure III.Upon decrease in temperature below the first predetermined value, thecontacts 24 are opened to terminate operation of the refrigeratingsystem I1 and the evaporator 2|, whereupon a mixture oiuncooledbutdoorand return air is delivered to the enclosure.

An increase in the cooling load of the enclosure beyond-the capacity ofthe evaporator 2| is represented by an increase in temperature to thesecond predetermined value at which both of the contacts 24 and 25 areclosed, resulting in operation of both refrigerating' systems and bothevaporators. The entire outdoor air streamis cooled I as before. In theduct II it is mixed with the air stream from' the enclosure and theportion of the mixture flows over and is cooled and dehumidiiled by theevaporator 22. The two portions of the mixed air stream passing overmixed air stream then in which the major aznar-11 If the temperature ofthe outdoor air drops to the predetermined value at which the contactsFigure 2 Provision may also be made for varying the amount of coolingeiiected in the chamber I4 and in the chamber I2, preferably by varyingthe effective evaporator cooling surface. For example, as illustrated inFig. 2, evaporators 2|a and 2lb are arranged in parallel in the chamberI4, and evaporators 22a and 22h are arranged in parallel in the chamberI2. It is to be understood, however, `that any other suitable provisionfor dividing the evaporator surface or for varying the effectiveevaporator surface may be provided. All of the evaporators are connectedto a common refrigerating `system 3|, including a variable capacitycompressor 32.

In this embodiment, the several evaporators are provided with solenoidvalves which control 'the evaporator 22 and through the by-pass 23,

respectively, then mix ,and are delivered to the enclosure Il throughthe lduct I5.

As thetemperature of the air in the enclosure I0 decreases below thesecond predetermined value, the contacts 25 open to terminate operationof the refrigerating system Il and the evapo-v rator 22, leaving therefrigerating. system I1 and evaporator 2| alone in operation to supplyC001- the supply of liquid refrigerant thereto. The solenoid valves forthe evaporators 2Ia, 2lb, 22a

and 22h are designated 33, 34, 35 and 36, re'

spectively. The thermostat 'I l is arranged to yenergize the solenoids33 to 36 in response to successively and slightly higher. predeterminedvalues representing substantially the tempera-ture desired to bemaintained in the enclosure III. The thermostat Ta is arranged to openthe circuit of-the solenoid 33 as the outdoor temperature decreases to avalue such that the entire cooling load can be taken care of without theevaporator 2 la. It opens the circuits oi solenoids 33 and 34 when theoutdoor temperature de'- creases to astill lower value such that theentire cooling load can be taken care of by the evaporators 22al and22h. Y

'Ihe operation of the compressor 32 is controlled in accordance with thetotal load oi' those Aevaporators which are in operation. It is providedwith Iseveral unloader mechanisms 31 which are adapted to render theassociated cylinders of the compressor ineffective to compressrefrigerant. They are controlled by a suitable control mechanism 38which is responsive to the pressure in thesuction line 33 connecting theoutlets of the several evaporators with the inlet of the compressor. Asthe suction pressure increases, the cylinders are successively loadedand as the suction pressure decreases, the cylinders are successivelyunloaded, thereby maintaining a substantially constant suction pressure.As the suction pressure reaches a predetermined minimum value, operationof the compressor is terminated by opening the motor circuit 4|. 'I'heparticular mechanism for controlling `the capacity of the compressorforms no part of the present invention; the invention contemplating anysuitable mechanism whereby compressor ca` pacity may be suitablycontrolled.

Figure Z-Operation .'I'he operation of the embodiment shown in Fig. 2is, infa general way, similar to thatof Fig. 1. Assuming the temperatureof the outdoor air to be suiliciently high to cause the thermostat T2 toclose the several contacts, the operation of the several evaporators isfcontrolled by the thermostat T1. As lthe temperature increases tosuccessively higher values, the several solenoid valves are sucessivelyopened in order to render the evaporators 2Ia, 2lb, 22a and 22h eectivein the order named. Conversely, upon decrease in temperature, theevaporators are rendered ineffective in the reverse order. The amount ofcooling is thus automatically controlled to maintain substantially thedesired temperature in the enclosure Il).

If either the evaporator 2Ia or both the evaporators 2Ia and 2lb arerendered inoperable by the thermostat T2, then the cooling load isVcarried by the remaining evaporators under control of the thermostatT1, as will be fully apparent from the description that has already beengiven.

While I have shown my invention in several forms, it will be obvious tothose skilled in the art that it is not so limited but is susceptible'ofvarious other changes and modications Without departing .from the spiritthereof, and I desire,

therefore, that only such limitations shall be placed thereupon as areimposed by the prior art or as are specically set forth in the appendedclaims.

What I claim is:

1. In an air conditioning system for an enclosure, the combination ofmeans for eifecting flow of a streamof air from the enclosure and' astream of outdoor air, mixing the two'streams and delivering the'mixedair stream to the enclosure, i'lrst means for cooling the outdoorairiirst and the second air cooling means automatically in response tosuccessively higher predetermined values of a heat load condition of theenclosure.

2. In an' air conditioning system for an enclosure, the combination ofmeans for effecting flow of a stream of air from the enclosure and astream of outdoor air, mixing 4the two streams and delivering the mixedair stream to the enclosure, first means-for cooling the outdoor airstream before mixing, second means forcooling` the mixed air stream,means :for-successively intiating operation of the first and the secondsuccessively higher predetermined values of a heat load condition of theenclosure, and means responsive to a predetermined minimum temperatureof the outdoor air Yfor terminating operation of the irst air coolingmeans independently v of the last-mentioned means.

3. In an air conditioning system 'for an enclosure, the combination ofmeans effecting iiowv of a stream of air from the enclosure and a.

and delivering the mixed air stream to the enc1osure,a plurality of aircooling elements for cooling the outdoor airstream beforemixing, aplurality of air cooling elements for cooling the mixed ai'r stream, meaincreases in a heat load condition of the enclosure for successivelyinitiating operationof the outdoor air cooling elements'and then themixed air coolingelements, and means responsive to successively loweroutdoor air temperatures for4 air stream before mixture, a secondevaporator disposed in the'path of the mixed air stream and a variablecapacity compressor connected to said evaporators; means forsuccessively initiating flow of refrigerant through the rst and thesecond evaporator automatically in response to successively highervalues of a heat load condition of the enclosure; and means responsiveto thesuction pressure in the refrigerating `system for controlling thecapacity or output of the compressor.

5. In an air conditioning system for an en`- closure, the combination ofmeans for 'effecting flow Aof a stream of air from the enclosure and astream of outdoor air, mixing'the two streams and delivering 4the mixedair stream to the 4enclosure; a refrigerating system including aplurality of evaporators disposed'in the path of the outdoor air streambefore mixture,a plurality of evaporators disposed in the path of themixed air stream, and a variable capacity compressor connected tosaid-evaporators; means responsive to successively higher values of aheat load condition of the enclosure for vsuccessively initiating flowof refrigerant through the outdoor air evaporators and then the mixedair evaporators; and means responsive to the suction pressure in therefrigerating system for controlling the capacity 'air cooling meansautomaticallyin response-to or output of the compressor.

6. Refrigerating apparatus comprising a plurality of evaporatorelements, individually operable valves for respectively controlling flowof refrigerant thereto, means including a common temperature-responsiveelement for controlling a plurality of said valves,l a. multi-cylindercompressor common to said evaporator elements, for withdrawing vaporizedrefrigerant therefrom, means for condensing the compressed refrigerantdischarged from the compressor, and meansfor varying the capacity oroutput of said compressor lin response to suction pressure by unloadingone stream of'outdoor air, mixing the two streams or more cylinders,whereby the Acomiiuessor output' is varied in accordance with evaporatorload while substantially constant pressure and temperature of therefrigerantis maintained in thel evaporator elements whose valves areopen. l

MCHARLES M; .ne

responsive to successive4 f

